The present invention relates generally to an engine. More particularly, the present invention relates to a valve-operating system for an engine.
Engines typically include one or more pistons that reciprocate within one or more cylinders. The pistons are coupled to a crankshaft that rotates in response to the reciprocation of the pistons. The crankshaft extends out of a housing and provides shaft power to drive one or more components (e.g., wheels, lawnmower blades, snow thrower auger, and the like).
Valves, generally two or more per cylinder, are disposed adjacent the combustion chamber and open at predefined points during the reciprocation of the piston. Typically, each cylinder includes at least an intake valve and an exhaust valve. The intake valve provides for the admission of an air/fuel charge for combustion. The exhaust valve opens to allow for the discharge of products of combustion. Many different valve-operating systems are available, including push-rod systems and overhead cam systems.
Overhead cam systems generally include a cam disposed on the same side of the combustion chamber as the valves, and on an opposite side of the combustion chamber then the piston. The cam is coupled to a cam shaft that is driven by the crankshaft to assure that it rotates at a speed that is proportional to the speed of the crankshaft. The cam shaft includes one or more cam lobes that actuate the valves, or an intermediate member such as a rocker arm, in response to rotation of the cam shaft. Generally, the cam shaft is coupled to the crankshaft via a belt drive (timing belt), a chain drive, or a direct gear connection.